JPH1069968A - Induction heating method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain insulation and dispense with enlargement of power source and its capacity by arranging a shield material made of a good conductive material between a site free of a heating site surrounded by a work coil of the heating site and the work coil. SOLUTION: An end face of a metal tube 1 is processed for a protrusion taper and an end face of a metal tube 2 is processed for a recess taper, respectively, both of which are engaged with each other by pinching an amorphous metal foil, and a heating site 4 in a limited range including a junction part 3 under pressure is heated. The site 4 is surrounded by a work coil 5, and a shield material 6 is arranged between a site out of the site 4 of the sites surrounded by the coil 5 and the coil 5. The shield material 6 is a good conductive material such as copper. When a current such as high-frequency current flows a winding 12 of the coil 5, an induction current flows the part 4, and the induction current flows the shield material 6 in the site out of the site 4. Consequently, the site 4 in the limited range in a lengthwise direction including the junction part 3 is selectively heated, and heating is restricted in the site out of the site 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of joining metal tubes such as steel pipes or metal rods such as steel bars in the lengthwise direction, such as heating during joining or heat treatment after joining. And a method and apparatus for inductively heating a restricted part of the apparatus.

[0002]

2. Description of the Related Art Metal pipes such as steel pipes or metal rods such as steel bars are butt-jointed in the longitudinal direction.
Welding such as IG welding and TIG welding, pressure welding, diffusion bonding and the like are known. Diffusion bonding includes a method in which an amorphous metal foil is interposed between both end faces, and elements contained in the foil are diffused into both materials.

[0003] In these joints, in the case of welding, heating for heat treatment after welding is required depending on the material. In the case of pressure welding or diffusion bonding, heating for bonding is required. Induction heating is widely used as the heating means, and an appropriate high frequency or low frequency is selected according to the required heating depth of the material to be heated.

[0004] By the way, in the case of heating at the time of joining or heat treatment after joining, if a base material other than the joining portion is heated, there is a problem that material deterioration such as a decrease in strength occurs.
It is desirable to limit the joints to a minimum necessary narrow range on both sides. As one of the means for limiting the range of the heating portion in the induction heating, it is conceivable to limit the induction current flowing through the material to be heated.

[0005] Japanese Patent Application Laid-Open No. Hei 2-301522 discloses an induction heating device used in a continuous annealing line for steel sheets, which includes a plurality of induction heating furnaces each comprising a solenoid type coil wound around a hollow heat insulating material. Which is provided with a magnetic shield plate. However, this magnetic shield plate suppresses the induced current generated in the adjacent solenoid type coil due to the mutual induction action, and does not limit the induced current flowing to the heating portion.

[0006]

In the induction heating of a metal tube or a metal rod, a portion surrounded by a work coil such as the above-mentioned solenoid type coil is heated. It is necessary to reduce the number of turns or to narrow the heating zone.

However, in order to increase the winding density of the work coil, there is a limitation in maintaining insulation between the windings. In addition, when the number of turns is reduced, a large current needs to be passed through the coil in order to pass an induced current required to heat the heated portion to a predetermined temperature, and the power supply must be large in capacity and size.

According to the present invention, when metal pipes such as steel pipes or metal rods such as steel bars are butt-joined in the length direction, the length in the length direction is limited, such as heating at the time of joining or heat treatment after joining. A method and apparatus for induction heating of a part, wherein there is no problem in maintaining insulation of a work coil,
It is another object of the present invention to provide a method and an apparatus which do not require an increase in the capacity and size of a power supply.

[0009]

According to the present invention, there is provided a method for inductively heating a limited portion of a metal tube or a metal rod in a longitudinal direction, wherein the heated portion is formed by a work coil. By arranging a shield member made of a good conductive material between the work coil and a part of the part surrounded by the work coil and deviating from the heated part, an induced current is applied to the heated part. An induction heating method characterized by flowing an induced current to the shield material at a portion deviating from the heating portion as well as flowing. Then, it is preferable to inject the cooling medium to a part deviating from the heating part.

According to another aspect of the present invention, there is provided an apparatus for inductively heating a limited portion of a metal tube or a metal rod in a longitudinal direction, the work coil having a work coil surrounding the heated portion. An induction heating apparatus characterized in that a shield member made of a good conductive material is disposed between the work coil and a part of the part surrounded by the work coil that is separated from the heating part. . And it is preferable that the cooling-medium injection device is arrange | positioned via the partition plate in the part deviated from the heating part.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of the present invention will be described by taking diffusion bonding of a metal tube as an example. FIG. 1 shows a cross section of a state where a metal tube 1 and a metal tube 2 are butt-joined. The end face of the metal tube 1 is processed into a convex taper, and the end surface of the metal tube 2 is processed into a concave taper,
Both are fitted with an amorphous metal foil (not shown) interposed therebetween, and the heating portion 4 in a limited range including the joint 3 is heated under pressure.

The heating portion 4 is surrounded by a work coil 5, and a shield member 6 is disposed between the work coil 5 and a portion of the portion surrounded by the work coil 5, the portion being outside the heating portion 4. The shield material 6 is made of a good conductive material such as copper.
When a current such as a high-frequency current flows through the winding 12 of the work coil 5 in this state, an induction current flows through the heating portion 4, and an induction current flows through the shield member 6 at a portion outside the heating portion.

Therefore, in the present embodiment, the heating portion 4 in the range limited in the length direction including the joint portion 3 is selectively heated, and the portion outside the heating portion 4 is suppressed from being heated. By setting the heated portion 4 to a range necessary for diffusion of the joint 3 and both sides thereof, only the minimum necessary range is heated to a required high temperature, and the temperature of the base material at a portion outside the heated portion 4 is suppressed. Therefore, it is possible to suppress material deterioration such as a decrease in the strength of the base material.

In the method of the present invention, the shielding material 6 is
In addition to being provided on both sides of the heating part 4 as in the example of FIG. 1, it may be provided on one side. For example, when the metal tube 2 is short and is joined to another member such as a flange, the work coil 5 is generally offset to the metal tube 1 side, and the shielding material 6 can be disposed on the metal tube 2 side. Disappears. In such a case, it is possible to suppress overheating of a portion deviating from the heated portion 4 by heat conduction to the flange or the like or by cooling the flange or the like. In the case where metal materials having different materials are joined to each other and only one metal material is likely to deteriorate due to heat, the shielding material 6 may be provided only on the material side.

In the diffusion bonding via the amorphous metal foil as in the present embodiment, the temperature of the heating portion 4 is 1200 in the case of steel.
1 ° C., and the range only needs to be 1 mm or more on each side from the joint 3. When a 45 ° taper is formed on the joint end surfaces of both the metal tubes 1 and 2 as in the example of FIG. The thickness may be set to be +3 mm or more.

Since the heating portion 4 is at such a high temperature,
In order to protect the work coil 5 and the shield member 6, a heat insulator 10 is wound around the metal tubes 1 and 2.
Further, when the shield member 6 is made of a good conductive material having a lower electric resistance than the material to be heated and is made of copper, there is a possibility that the shield member 6 may be melted. Therefore, the shield member 6 is cooled by winding a water cooling pipe 11 as shown in FIG.

Next, an example of a preferred embodiment of the method of the present invention is shown in FIG. A cooling medium spraying device 7 is disposed at a position outside the heating region 4, and a cooling medium such as water is sprayed on the metal pipes 1 and 2. A partition plate 8 is provided in a ring shape at the boundary between the heating part 4 and the cooling medium injection part. The cooling medium ejecting device 7 is disposed outside the shielding material 6, and injects the cooling medium to the metal tubes 1 and 2 through the through holes 9 provided in the shielding material 6. FIG. 4 shows a perspective view of the shield member 6. In this case, the shield member 6 does not require the water cooling pipe 11 as shown in FIG. Further, as shown in FIG. 2, the heat insulating material 10 is provided only in the range of the heating part 4.

According to such a preferred embodiment, the temperature of the base material at the portion deviated from the heated portion 4 is further suppressed from being raised, and the material deterioration such as a decrease in strength can be further suppressed. Further, even after the induction heating is completed, rapid cooling after the heating can be performed by continuing the cooling by the cooling medium injection device 7 continuously.

The position of the cooling medium injection device 7 is as follows.
The present invention is not limited to this example, and may be inside the shield member 6. However, when it is set inside, if there is a possibility that the shielding material 6 is melted, a cooling means as shown in FIG. 3 is necessary. In addition, depending on the heating conditions and the material of the material to be heated, the cooling medium injection device 7 can be disposed at a position separated from the heating portion 4. Further, as shown in FIG. 5, the shield material 6 may have a cooling medium injection function. That is, the shielding material 6 is made hollow, and the injection hole 13 is provided on the inner side, so that the heating portion 4
A cooling medium such as water may be jetted to a portion deviated from the outside.

The method of the present invention can be applied to diffusion bonding between metal rods in addition to the above-described example of the metal tube. Further, the present invention is not limited to diffusion bonding, and can be applied to a case where the metal tube 1 and the metal tube 2 or metal rods are pressed together or a heat treatment after welding.

According to the method of the present invention, the winding density of the work coil is set within a range in which there is no problem in maintaining the insulation, and it is not necessary to reduce the number of turns. Therefore, the power supply is limited without increasing the capacity and size. It is possible to heat a small area of the heated portion to a required temperature for joining. In addition, in a portion deviating from the heated portion, material deterioration such as a decrease in the strength of the base material can be suppressed.

Diffusion bonding between amorphous metal foils as shown in FIGS. 1 and 2 can be performed at lower cost and easier than other bonding means such as MIG welding, TIG welding, or pressure welding. It is suitable for the on-site construction of pipes or the joining of steel pipes and steel bars in various construction sites. By adopting the method of the present invention, the heating that suppresses the deterioration of the material of the base material on both sides of the joint can be performed by induction heating using a small power source.

Next, the apparatus according to the present invention, as shown in FIG.
It has a work coil 5 surrounding the heating part 4, and a shield member 6 made of a good conductive material is disposed between the work coil 5 and a part deviated from the heating part 4 in a part surrounded by the work coil 5. Have been. Then, as shown in FIG. 2, it is preferable that a cooling medium ejecting device 7 is provided via a partition plate 8 at a portion separated from the heating portion 4. The operation of the device of the present invention is as described in detail in the method of the present invention.

In the present invention, the material to be heated 1 is not limited to the above-described circular shape in cross section, but may be applied to various shapes such as a square shape. In that case, winding 1
The shape 2 is adapted to the shape of the material 1 to be heated.

[0025]

【Example】

Invention Example 1: Steel pipes were diffusion bonded by the method of the invention using the apparatus of the invention as shown in FIGS. The steel pipe is STK400 specified in JIS G 3444, outer diameter 26
It has a size of 4.4 mm, an inner diameter of 228.8 mm and a thickness of 17.8 mm.
A convex taper and a concave taper having an inclination angle of 45 ° as shown in FIG. 1 were machined on the ends of both steel pipes, fitted with an amorphous metal foil therebetween, and heated with a load of about 900 kg. The amorphous metal foil has a composition of Fe-9 wt% Si-1.5 wt% B, and has a thickness of 30 μm.

The work coil 5 has an inner diameter of 350 mm, a length of 200 mm, and has 10 turns. The shield material 6 is made of copper.
A water-cooled pipe 11 was brazed to an outer diameter of 330 mmφ, an inner diameter of 290 mm, and a length of 80 mm, and was arranged at both ends of the work coil 5 as shown in FIG. Therefore, the interval between the two shield members 6 was 40 mm, and the range of this 40 mm was defined as the heating portion 4, and the joint 3 was located at the center of the heating portion 4 as shown in FIG. 1. Also, the heat insulating material 10
, A cylindrical kao wool having an initial thickness of 15 mm was attached to a steel pipe.

The power supply connected to the work coil 5 is a small-sized, high-frequency power supply with a maximum output of 50 kW and a frequency of 8 kHz. With this power source, the secondary power is reduced to 40 kW (700
V, 60A, 95% efficiency)
After heating to 1200 ° C. at a temperature rising rate of ° C./sec and holding for 5 minutes, the power was turned off and allowed to cool.

Inventive Example 2: Using the apparatus of the present invention as shown in FIG. 2 and FIG.
The same steel pipe as described above was diffusion bonded with the same amorphous metal foil interposed therebetween. The work coil 5 is the same as that of the first embodiment of the present invention, and the dimensions of the shield member 6 are the same as those of the first embodiment of the present invention. Induction heating was performed under the same conditions. Comparative Example: In FIG. 1, a steel pipe was joined in the same manner as in Example 1 of the present invention except that the shielding material 6 was not used.

For each of the above inventive examples and comparative examples, a tensile test piece was taken from the sample divided into eight pieces in the circumferential direction after joining, with the joint 3 at the center, and a tensile test was performed. As a result, the tensile strength was 400 MPa or more in each case, and the joining strength was good and no difference was observed. However, a difference was observed in the 0.2% proof stress. Inventive Example-1 ... 300 to 320 MPa Inventive Example-2 ... 310 to 330 MPa Conventional Example ... 230 to 260 MPa. The 0.2% proof stress of the base material not affected by heat is 35
Since the pressure is about 0 MPa, in the conventional example, the strength of the base material was significantly reduced due to the influence of heat, whereas in the example of the present invention, the strength was able to be suppressed.

[0030]

According to the present invention, in the case where metal pipes such as steel pipes or metal rods such as steel bars are butt-joined in the longitudinal direction, the lengthwise restriction such as heating at the time of joining or heat treatment after joining is performed. A method and apparatus for induction heating of a part that has been heated without narrowing the winding range of the work coil, because it is possible to selectively heat a narrow part of the heated part,
Since the winding density is set within a range where there is no problem in maintaining the insulation and the number of turns does not need to be reduced, it is not necessary to increase the capacity and size of the power supply. Then, it is possible to heat the heated portion in a limited narrow range to a required temperature, and to suppress the material deterioration such as a decrease in the strength of the base material in the portion outside the heated portion. Therefore, it is suitable for the on-site construction of oil country tubular goods or the joining and heat treatment of steel pipes, steel rods, and the like at the site of various construction works.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of the method and apparatus of the present invention.

FIG. 2 is a cross-sectional view showing another example of the method and apparatus of the present invention.

FIG. 3 is a perspective view showing an example of a shielding material in the method and the device of the present invention.

FIG. 4 is a perspective view showing another example of the shielding material in the method and the device of the present invention.

FIG. 5 is a cross-sectional view illustrating another example of the method and apparatus of the present invention.

[Explanation of symbols]

 1, 2, metal pipe 3, joint 4, heating part 5, work coil 6, shielding material 7, cooling medium jetting device 8, partition plate 9, through hole 10, heat insulating material 11, water cooling pipe 12, winding 13, etc. Injection hole

 ──────────────────────────────────────────────────の Continued on the front page (72) Eiji Tsuru, Inventor 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division

Claims (4)

[Claims] 1. A method for inductively heating a limited portion in a longitudinal direction of a metal tube or a metal rod, wherein the heated portion is surrounded by a work coil, and the heating is performed in the portion surrounded by the work coil. By arranging a shield material made of a good conductive material between the part deviated from the part and the work coil, an induced current flows through the heated part, and at the part deviated from the heated part, the shield material is applied to the shield material. An induction heating method characterized by flowing an induction current. 2. The induction heating method according to claim 1, wherein a cooling medium is injected to a portion deviated from the heating portion. 3. An apparatus for inductively heating a limited portion in a longitudinal direction of a metal tube or a metal rod, the device having a work coil surrounding a heated portion, and a portion of the portion surrounded by the work coil. An induction heating device, wherein a shield member made of a good conductive material is provided between a portion deviating from the heating portion and the work coil. 4. The induction heating device according to claim 3, wherein a cooling medium ejecting device is provided at a portion separated from the heating portion via a partition plate.